U.S. patent application number 12/737539 was filed with the patent office on 2011-06-30 for torque wrench.
This patent application is currently assigned to TOHNICHI MFG CO., LTD.. Invention is credited to Shozo Aikawa, Kyo Kan, Naoya Masuda, Tomohiro Ogata, Hiroshi Tsuji.
Application Number | 20110154961 12/737539 |
Document ID | / |
Family ID | 42982274 |
Filed Date | 2011-06-30 |
United States Patent
Application |
20110154961 |
Kind Code |
A1 |
Kan; Kyo ; et al. |
June 30, 2011 |
TORQUE WRENCH
Abstract
To make improvements in torque wrenches with a torque limiter
that uses a cam mechanism and to provide a torque wrench that
realizes more stable operation and is capable of highly precise
tightening. In a torque wrench with a torque limiter that uses a
cam mechanism, a solid columnar roller member 14 is engaged with a
cam part 7 of a cam shaft 8 such that it is rotatably supported by
a roller support lever member 12 mounted in a head portion 2 such
as to be rotatable around a support shaft 16 and such that it is
pressed against the cam part 7 by a spring force transmitting rod
18 biased by a torque setting spring. The roller support lever
member 12 is configured such that the distance r2 from the support
shaft 16 to a point of application of force of the spring force
transmitting rod 18 is longer than the distance r1 from the support
shaft 16 to the roller member 14.
Inventors: |
Kan; Kyo; (Tokyo, JP)
; Aikawa; Shozo; (Tokyo, JP) ; Ogata;
Tomohiro; (Tokyo, JP) ; Masuda; Naoya; (Tokyo,
JP) ; Tsuji; Hiroshi; (Tokyo, JP) |
Assignee: |
TOHNICHI MFG CO., LTD.
Tokyo
JP
|
Family ID: |
42982274 |
Appl. No.: |
12/737539 |
Filed: |
February 16, 2010 |
PCT Filed: |
February 16, 2010 |
PCT NO: |
PCT/JP2010/000922 |
371 Date: |
March 7, 2011 |
Current U.S.
Class: |
81/478 |
Current CPC
Class: |
B25B 13/465 20130101;
B25B 23/1427 20130101 |
Class at
Publication: |
81/478 |
International
Class: |
B25B 23/143 20060101
B25B023/143 |
Foreign Application Data
Date |
Code |
Application Number |
Apr 16, 2009 |
JP |
2009-100061 |
Apr 16, 2009 |
JP |
2009-100062 |
Jan 18, 2010 |
JP |
2010-007917 |
Claims
1. A torque wrench comprising: a head portion having a cylindrical
cam shaft rotatably disposed with a plurality of cam parts formed
on an outer circumference thereof, the cam parts each having a
torque transmitting cam surface and a torque non-transmitting cam
surface, and a torque transmission shaft coaxially disposed inside
the cam shaft for tightening an object to be tightened via a
ratchet mechanism; a tubular lever fixed to a rear end portion of
the head portion and accommodating therein a spring force
transmitting rod biased by a torque setting spring; a roller member
engaged with the cam part; and a roller support lever member
rotatably mounted in the head portion via a support shaft for
rotatably supporting the roller member and for applying the spring
force via the spring force transmitting rod to the roller member so
as to cause a tightening reaction force to be applied to the roller
member, wherein the roller support lever member is configured such
that a distance from the support shaft to a point of application of
force of the spring force transmitting rod is longer than a
distance from the support shaft to the roller member.
2. The torque wrench according to claim 1, wherein the roller
member is solid and columnar.
3. The torque wrench according to claim 1, wherein the cam part is
configured such that, in a position where the roller member is
stationary and in engagement therewith, a vector along a normal
direction of a reaction force applied to the roller member is
displaced by an angle .theta. in a tightening direction relative to
a base line connecting an axial center of the roller member and an
axial center of the support shaft.
4. The torque wrench according to claim 1, wherein the cam part is
configured such that, in a position where the roller member is
stationary and in engagement therewith, a vector along a normal
direction of a reaction force applied to the roller member is
displaced by an angle .theta. larger than 0.degree. and smaller
than 45.degree. in a tightening direction relative to a base line
connecting an axial center of the roller member and an axial center
of the support shaft.
5. The torque wrench according to claim 1, wherein the cam shaft
disposed inside the head portion is formed with circumferential
grooves on an outer circumference at both axial ends thereof, with
a plurality of steel balls being disposed between each of the
circumferential grooves and an inner circumferential wall surface
of the head portion opposite and spaced apart therefrom to form
radial bearings, and wherein the steel balls are made abut on an
inner wall surface of the head portion that is axially above an
axial outer end of the cam shaft so as to form a gap between the
axial outer end of the cam shaft and the axial inner wall surface
of the head portion.
6. The torque wrench according to claim 1, further comprising a
rolling bearing including a plurality of rolling elements disposed
between an inner race and an outer race, the rolling bearing being
disposed at both axial ends of the cam shaft between an inner
circumferential surface of the head portion and the cam shaft
disposed inside the head portion.
7. The torque wrench according to claim 1, wherein a steel ball
forming a thrust bearing is disposed between one end face of the
transmission shaft opposite from a side engaged with the object to
be tightened and an inner wall surface of the head portion facing
the one end face.
8. The torque wrench according to claim 1, wherein steel balls
forming thrust bearings are disposed between both axial ends of the
support shaft of the roller support lever member and inner wall
surfaces of the head portion, respectively.
9. The torque wrench according to claim 1, wherein the spring force
transmitting rod has its both ends formed in a spherical shape,
with engaging recesses that engage with the rod such as to allow
pivotal movement of the rod being formed in the roller support
lever member and in an abutting member on the side of the torque
setting spring, respectively.
10. The torque wrench according to claim 1, further comprising a
sensor for detecting a change in inclination of the spring force
transmitting rod relative to an axial direction of the lever upon
rotation of the roller support lever member, as the roller member
moves along a torque transmitting cam surface of the cam part
toward a cam top by a tightening reaction force.
11. The torque wrench according to claim 1, further comprising a
coupling mechanism for coupling a distal end portion of the lever
to a rear portion of the head portion by screw coupling, wherein
the coupling mechanism includes threaded portions respectively
formed to threaded tube portions respectively formed at the rear
end portion of the head portion and at the distal end portion of
the lever to be internally or externally screwed to each other, and
a cylindrical positioning member abutting on and pressing a distal
end portion of one of the threaded tube portions on the internal or
external side against the other one of the threaded tube portions,
and wherein the positioning member is screwed to a threaded portion
of the other threaded tube portion and abuts and makes pressure
contact with a distal end face of the one threaded tube portion so
as to fix the head portion and the lever at an arbitrary position
in a circumferential direction around an axial center of the
lever.
12. The torque wrench according to claim 1, further comprising a
coupling mechanism for coupling a distal end portion of the lever
to a rear portion of the head portion by screw coupling, wherein
the coupling mechanism includes threaded portions respectively
formed to threaded tube portions respectively formed at the rear
end portion of the head portion and at the distal end portion of
the lever to be internally or externally screwed to each other, and
a cylindrical positioning member abutting on and pressing a distal
end portion of one of the threaded tube portions on the internal or
external side against the other one of the threaded tube portions,
and wherein the positioning member is screwed to a threaded portion
of the other threaded tube portion and makes tapered engagement
with a distal end portion of the one threaded tube portion so as to
fix the head portion and the lever at an arbitrary position in a
circumferential direction around an axial center of the lever.
13. The torque wrench according to claim 12, wherein the
positioning member of the coupling mechanism is screwed to an inner
circumferential threaded portion of the other threaded tube portion
into which the one threaded tube portion is internally screwed, so
that the positioning member makes tapered engagement with an inner
circumferential surface of the distal end portion of the one
threaded tube portion to spread and press the distal end portion of
the one threaded tube portion against the inner circumferential
surface of the one threaded tube portion, whereby the head portion
and the lever are fixed to each other.
14. The torque wrench according to claim 12, wherein the
positioning member of the coupling mechanism is screwed to an outer
circumferential threaded portion of the other threaded tube portion
onto which the one threaded tube portion is externally screwed, so
that the positioning member makes tapered engagement with an outer
circumferential surface of the distal end portion of the one
threaded tube portion to tighten the distal end portion of the one
threaded tube portion onto the outer circumferential surface of the
other threaded tube portion, whereby the head portion and the lever
are fixed to each other.
15. The torque wrench according to claim 1, comprising a sensor
that detects an inclining movement of the spring force transmitting
rod caused by a rotation of the roller support lever member as the
roller member engages with and traces the cam part.
16. The torque wrench according to claim 15, wherein the coupling
mechanism arbitrary determines positions of the sensor and the
spring force transmitting rod in a circumferential direction around
an axial center of the lever, whereby the head portion and the
lever are positioned and fixed.
17. The torque wrench according to claim 16, wherein the coupling
mechanism positions and fixes the head portion and the lever at a
position where the sensor is activated when the rod reaches a
maximum inclined position.
Description
TECHNICAL FIELD
[0001] The present invention relates to a torque wrench that can
tighten a fatener such as a bolt or nut with a specified torque
byway of a torque limiter using a cam mechanism that is activated
when the specified torque is reached.
BACKGROUND ART
[0002] Conventionally, a torque wrench with a torque limiter that
uses a cam mechanism is known, which has a configuration in which a
cylindrical head portion is attached to a distal end of a
cylindrically formed lever. In the head portion, transmission shaft
with a square shaft portion, to which an engaging portion such as a
hexagonal socket or the like to engage with a fastener such as a
bolt or nut is removably attached, is mounted via a ratchet
mechanism such that the shaft can rotate only in one direction.
When a tightening force is manually applied to the lever and the
tightening torque reaches a specified torque, the torque limiter
disposed between the head portion and a distal end portion of the
lever is activated, so that the fastener is released from the
tightening force transmitted thereto (Patent Literature 1).
[0003] In the configuration of this torque limiter using a cam
mechanism, a cylindrical cam shaft having a plurality of cam parts
continuously formed in the circumferential direction on the outer
circumferential surface thereof is rotatably disposed inside a
cylindrically formed head body, while a cam follower in the form of
a columnar roller is pressed against the cam part via a thrust pad
mounted to a distal end portion of a torque adjusting spring
disposed inside the cylindrical lever. The roller can move in the
axial direction of the lever to abut on an inner circumferential
surface of the lever. A plurality of ratchet teeth are formed in
the circumferential direction on the inner circumferential surface
of a shaft hole in the cam shaft, while a main shaft portion of the
transmission shaft is rotatably disposed in the shaft hole, so that
ratchet claws attached on the outer circumference of the main shaft
portion engage with the ratchet teeth. A rotation imparted to the
cam shaft in a tightening direction causes the ratchet claws to
engage with the ratchet teeth to rotate the transmission shaft,
whereby the fastener such as a bolt is tightened.
[0004] The cam part of the cam shaft forming the torque limiter is
configured such that a torque transmitting cam surface which is a
steep slope and a torque non-transmitting cam surface which is a
gentle slope are formed on both sides of a cam top. The roller
waits in a state where it is pressed against a torque transmitting
cam surface of the cam part. A tightening force transmitted via the
lever to the roller causes the camshaft to rotate in the tightening
direction via the torque transmitting cam surface. As the
tightening force to the fastener such as a bolt increases, the
reaction force from the torque transmitting cam surface to the
roller increases, whereby the roller moves toward the cam top
against the spring force of the torque adjusting spring. When the
roller goes over the cam top, the roller stops applying the force
that rotates the camshaft in the tightening direction, whereby the
user is notified that the specified torque has been reached.
PRIOR ART LITERATURE
[Patent Literature]
[0005] [Patent Literature 1] Specification of British Patent
Application Laid-Open No. 2148767A
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0006] In the torque limiter using the conventional cam mechanism
described above, the spring force of the torque adjusting spring
for determining a specified torque acts directly on the roller. As
the spring force of the torque adjusting spring is increased in
proportion to the value of the specified torque, during a
tightening operation, as the roller receives the reaction force
from the torque transmitting cam surface and moves against the
spring force of the torque adjusting spring in contact with an
inner circumferential wall surface of the lever, it makes high
friction contact with the inner wall surface of the lever, and also
with the thrust pad. This causes wear on the roller, thrust pad,
and inner wall surface of the lever, and there was a worry that
this would have adverse effects such as causing the torque limiter
to be activated outside a tolerance range of a correct specified
torque, or leading to instabilities in the operation.
[0007] An object of the present invention is to make a further
improvement in torque wrenches having a torque limiter that uses a
cam mechanism, and to provide a torque wrench that can realize more
stable operation and is capable of highly precise tightening.
Means for Solving the Problems
[0008] The torque wrench that achieves the object of the present
invention is configured to include: a head portion having a
cylindrical cam shaft rotatably disposed with a plurality of cam
parts formed on an outer circumference thereof, the cam parts each
having a torque transmitting cam surface and a torque
non-transmitting cam surface, and a torque transmission shaft
coaxially disposed inside the cam shaft for tightening an object to
be tightened via a ratchet mechanism; a tubular lever fixed to a
rear end portion of the head portion and accommodating therein a
spring force transmitting rod biased by a torque setting spring; a
roller member engaged with the cam part; and a roller support lever
member rotatably mounted in the head portion via a support shaft
for rotatably supporting the roller member and for applying the
spring force via the spring force transmitting rod to the roller
member so as to cause a tightening reaction force to be applied to
the roller member, wherein the roller support lever member is
configured such that a distance from the support shaft to a point
of application of force of the spring force transmitting rod is
longer than a distance from the support shaft to the roller member.
The roller member may have a solid, columnar structure.
[0009] Another configuration of the torque wrench that achieves the
object of the present invention includes, in the torque wrench
configured as described above, a coupling mechanism for coupling a
distal end portion of the lever to a rear portion of the head
portion by screw coupling, wherein the coupling mechanism includes
threaded portions respectively formed to threaded tube portions
respectively formed at the rear end portion of the head portion and
at the distal end portion of the lever to be internally or
externally screwed to each other, and a cylindrical positioning
member abutting on and pressing a distal end portion of one of the
threaded tube portions on the internal or external side against the
other one of the threaded tube portions, and wherein the
positioning member is screwed to the threaded portion of the other
threaded tube portion and makes tapered engagement with a distal
end portion of the one threaded tube portion so as to fix the head
portion and the lever at an arbitrary position in a circumferential
direction around an axial center of the lever.
[0010] A further configuration of the torque wrench that achieves
the object of the present invention includes, in either of the
above-described configurations, a sensor that detects an inclining
movement of the spring force transmitting rod caused by a rotation
of the roller support lever member as the roller member engages
with and traces the cam part.
[0011] The coupling mechanism positions and fixes the head portion
and the lever in a circumferential direction around an axis of the
lever, with the position of the sensor and the position of the
spring force transmitting rod being set at a predetermined
position.
Effects of the Invention
[0012] According to the present invention, the spring force of the
torque setting spring is applied via the roller support lever
member to the roller member engaging with the cam part, with the
distance between the support shaft and the point of application of
force of the spring force transmitting rod being longer than the
distance between the support shaft and the roller member. It is
thus possible to make the spring force of the torque setting spring
smaller relative to the reaction force applied to the roller member
for the torque limiter to be activated, whereby the torque setting
spring can be made smaller and lighter, which in turn leads to a
reduction in size and weight of other components, and in turn of
the entire torque wrench.
[0013] According to the invention as set forth in claim 2, the
roller member is solid and columnar, whereby the effects of
deformation due to the force in the radial direction applied during
the tightening can be eliminated. Furthermore, the thickness of the
cam part is substantially matched with the axial length of the
roller member, and the roller member is supported by the roller
support lever member over an entire axial length thereof, so that
surface pressure on the roller member is reduced and the roller
member can be rotated smoothly.
[0014] According to the inventions as set forth in claims 3 and 4,
the torque limiter can be activated reliably with an increase in
the tightening force.
[0015] According to the invention as set forth in claim 5, the cam
shaft can be rotated smoothly.
[0016] According to the invention as set forth in claim 6, the
transmission shaft can be rotated smoothly.
[0017] According to the invention as set forth in claim 7, the
roller support lever member can be rotated smoothly.
[0018] According to the invention as set forth in claim 8, the
spring force transmitting rod can be inclined smoothly with an
increase in the tightening force.
[0019] According to the invention as set forth in claim 9, the
activation of the torque limiter can be electrically detected
without providing an additional special mechanism.
[0020] According to the invention as set forth in claim 10, the
head portion and lever can be fixed rigidly and with a simple
structure at an arbitrary position in a circumferential direction
around the axial center of the lever.
[0021] According to the invention as set forth in claim 11, in
addition to the effect of the invention according to claim 10
described above, accidental loosening of the positioning member can
be prevented as the positioning member is not exposed to the
outside of the torque wrench.
[0022] According to the invention as set forth in claim 12,
tightening of the positioning member can be made easily.
[0023] According to the invention as set forth in claim 13, the
sensor can be activated without requiring any special mechanism,
because of the use of the spring force transmitting rod as means
for electrically detecting a specified torque being reached in
synchronization with activation of the torque limiter.
[0024] According to the inventions as set forth in claims 14 and
15, the head portion and the lever can be positioned and fixed
while taking into consideration the sensor and the plane in which
the spring force transmitting rod inclines, so that the sensor can
output a detection signal indicative of the tightening torque
having reached the specified torque at the same time when the
torque limiter is activated.
BRIEF DESCRIPTION OF THE DRAWINGS
[0025] FIG. 1 is a sectional view showing the entire configuration
of a torque wrench according to Embodiment 1 of the present
invention.
[0026] FIG. 2 is an enlarged view of a head portion in FIG. 1.
[0027] FIG. 3 is a sectional view taken along the line A-A and
viewed in the direction of the arrows in FIG. 2.
[0028] FIG. 4 is an external perspective view of the head portion
of FIG. 1 to FIG. 3.
[0029] FIG. 5 is a diagram along the line B-B and viewed in the
direction of the arrows in FIG. 3, showing vectors of the
tightening force acting on the torque limiter of FIG. 4.
[0030] FIG. 6 is a partial sectional view of a torque wrench
according to Embodiment 2, showing a state where the switch is not
activated.
[0031] FIG. 7 is a partial sectional view of a torque wrench
according to Embodiment 2, showing a state where the switch is
activated.
[0032] FIG. 8 is a sectional view showing the entire configuration
of a torque wrench according to Embodiment 3.
[0033] FIG. 9 is a partially cut-away sectional view showing the
detail of a coupling mechanism coupling the head and the lever of a
torque wrench according to Embodiment 4.
[0034] FIG. 10 is a partially cut-away sectional view showing the
detail of a coupling mechanism coupling the head and the lever of a
torque wrench according to Embodiment 5.
[0035] FIG. 11 is a partially cut-away sectional view showing the
detail of a coupling mechanism coupling the head and the lever of a
torque wrench according to Embodiment 6.
MODES FOR CARRYING OUT THE INVENTION
[0036] The present invention will be hereinafter described based on
embodiments shown in the drawings.
Embodiment 1
[0037] FIG. 1 is a sectional view showing the entire configuration
of a torque wrench according to Embodiment 1 of the present
invention, FIG. 2 is a view showing a head portion in FIG. 1, FIG.
3 is a sectional view taken along the line A-A and viewed in the
direction of the arrows in FIG. 2, and FIG. 4 is an external
perspective view of the torque limiter that uses the cam mechanism
shown in FIG. 1 to FIG. 3.
[0038] The torque wrench 1 of the present embodiment is a torque
tool having a mechanical torque limiter that uses a cam mechanism
so that a fastener such as a bolt or nut can be tightened with a
specified torque.
[0039] The torque wrench 1 is composed of a head portion 2 that
engages with a fastener (hereinafter described as a bolt by way of
example), and a cylindrical lever 4. A grip 6 for a user to hold on
during a tightening operation is attached at the rear end of the
lever 4. The head portion 2 includes a substantially square
parallelepiped case portion 3a with a curved surface at the distal
end thereof and a threaded tube portion 3b formed integrally to the
rear end of the case portion 3a and having a threaded portion on an
inner circumferential surface thereof. Threading a threaded portion
formed on the outer circumference at the distal end of the lever 4
into the threaded tube portion 3b couples the case portion 3a of
the head portion 2 and the lever 4, whereby the lever 4
communicates with the case portion 3a.
[0040] Assuming that the axial direction of the lever 4 is X-axis,
the up and down direction of the case portion 3a is Z-axis, and the
direction orthogonal to both X-axis and Z-axis is Y-axis, the case
portion 3a of the head portion 2 is open at one end in the Z-axis
direction, this end being closed by a lid 3c. A cam shaft 8 formed
with a shaft hole 8a in the center at the distal end thereof is
disposed inside the case portion 3a.
[0041] The cam shaft 8 formed with the shaft hole 8a includes an
upper circumferential groove 8b and a lower circumferential groove
8c that are curved recesses formed on the outer circumference at
both ends of the shaft portion thereof extending in the Z-axis
direction. A plurality of cam parts 7 (six in the present
embodiment) are equally spaced along the circumferential direction
between the upper and lower circumferential grooves 8b and 8c. A
circular hollow part 3e concentric with the cam shaft 8 is formed
in an upper wall portion 3d of the case portion 3a, with a
plurality of steel balls 9a substantially snugly arranged between
an inner circumferential wall surface of the hollow part 3e and the
upper circumferential groove 8b formed at the upper end of the cam
shaft 8, thereby forming a radial bearing. The steel balls 9a abut
also against an upper inner wall surface of the hollow part 3e so
as to function as a thrust bearing, too. The hollow part 3e
includes a shallow hollow part 3f forming a gap between itself and
the upper end of the cam shaft 8.
[0042] The lid 3c is formed with a circular hollow part 3g
concentric with the cam shaft 8, with a plurality of steel balls 9b
substantially snugly arranged between an inner circumferential wall
surface of the hollow part 3g and the lower circumferential groove
8c formed at the lower end of the cam shaft 8, thereby forming a
radial bearing. The steel balls 9b abut also against a lower inner
wall surface of the hollow part 3g so as to function as a thrust
bearing, too. The hollow part 3g includes a shallow hollow part 3h
forming a gap between itself and the lower end of the cam shaft 8.
The diameter of the steel balls 9a and 9b can be made as close as
possible to the depth of the hollow parts 3e and 3g as shown in
FIG. 3, which in turn allows the pressure receiving area of the
upper and lower circumferential grooves 8b and 8c relative to the
steel balls 9a and 9b to be increased. The Hertzian stress, which
is a stress applied from the steel balls 9a and 9b, can be
accordingly reduced, whereby wear of the radial bearings can be
reduced.
[0043] Ratchet teeth 8d are formed on the inner circumferential
surface of the shaft hole 8a of the cam shaft 8 as shown in FIG. 4,
with a main shaft 11a of a transmission shaft 11 being inserted in
the shaft hole 8a. A pair of ratchet claws 10 symmetrically
arranged to a center axis on the main shaft 11a of the transmission
shaft 11 is biased by ratchet springs (not shown) to engage with
the ratchet teeth 8d. When the cam shaft 8 turns in a clockwise
direction, the transmission shaft 11 turns integrally therewith. A
square shaft 11b is formed to the distal end of the transmission
shaft 11 such as to extend through the lid 3c so that a socket (not
shown) or the like can be removably attached thereto. A steel ball
9c that forms a thrust bearing is disposed between the end face of
the main shaft 11a and the hollow part 3f.
[0044] The plurality of cam parts 7 formed on the outer
circumference of the cam shaft 8 are configured such that torque
transmitting cam surfaces 7a which are steep slopes and torque
non-transmitting cam surfaces 7b which are gentle slopes are formed
on both sides of cam tops.
[0045] On the other hand, a substantially square parallelepiped
roller support lever member 12 that forms a link mechanism is
mounted in a rear part of the case portion 3a such as to be
pivotable around a support shaft 16 whose axis coincides with the
Z-axis direction. The roller support lever member 12 is formed with
substantially the same thickness as the thickness in the Z-axis
direction of the cam parts 7, with the support shaft 16 being
mounted at one end in the lengthwise direction thereof. On one face
side of the roller support lever member 12 opposite the cam part 7,
a solid columnar roller member 14 which acts as a cam follower is
rotatably held in a bearing recess 12a formed in a concave shape.
This bearing recess 12a has an inner radial surface with an inside
diameter that is substantially the same as the outside diameter of
the roller member 14, so that the roller member 14 abuts on a cam
surface of the cam part 7 as it rotates.
[0046] The roller support lever member 12 is further formed with a
pivot recess 12b such as to face the shaft hole of the threaded
tube portion 3b. This pivot recess 12b is formed at a position a
longer distance from the support shaft 16 as a starting point than
the center position of the roller member 14 in the lengthwise
direction of the roller support lever member 12.
[0047] Inside the lever 4, a torque setting spring 22 on the rear
end side is disposed between a rod seat 20 and an adjusting nut 21.
A turning operation from the rear end of the lever 4 of a torque
adjusting screw rod 24 threaded in the adjusting nut 21 advances
the adjusting nut 21 along the thread forward or backward in the
axial direction, thereby adjusting the spring pressure applied to
the rod seat 20.
[0048] The rod seat 20 is formed with a pivot recess 20a facing the
pivot recess 12b of the roller support lever member 12. A spring
force transmitting rod 18 is disposed between the pivot recess 20a
of the rod seat 20 and the pivot recess 12b of the roller support
lever member 12. Both ends 18a and 18b of the spring force
transmitting rod 18 are formed spherical (hereinafter "spherical
end"), so that they can abut on the pivot recesses 12b and 20a,
following a displacement in Y-axis direction and Z-axis direction,
if any, of the positions relative to each other of the pivot
recesses 12b and 20a in the X-axis direction.
[0049] In a non-tightened state in which the torque wrench 1 is not
tightening a bolt, the roller member 14 is pressed against a base
part of a torque transmitting cam surface 7a of the cam part 7 by
the spring force of the torque setting spring 22 applied from the
spring force transmitting rod 18 via the roller support lever
member 12. At this position, the roller member 14 is stationary and
stably held on the cam part 7. In this stationary state, the spring
force transmitting rod 18 is oriented parallel to the X-axis. The
roller support lever member 12 is formed with bearing recesses 26
in the upper and lower faces thereof, respectively, in which steel
balls 25 fit. These upper and lower steel balls 25 abut on the
inner faces of the case portion 3a and the lid 3c so as to position
the roller support lever member 12 in the Z-axis direction, as well
as enable smooth rotation of the roller support lever member 12
around the support shaft 16.
[0050] From the non-tightened state in which the roller support
lever member 12 is held stationary, as the bolt tightening starts,
the tightening force applied to the lever 4 is transmitted from the
support shaft 16 to the roller support lever member 12, and applied
from the roller member 14 to the torque transmitting cam surface 7a
of the cam part 7. As the bolt is further tightened, the roller
support lever member 12 receives a rotating force in the
counterclockwise direction around the support shaft 16 due to a
reaction force applied from the torque transmitting cam surface 7a
to the roller member 14. The roller support lever member 12, due to
the leverage principle, moves the spring force transmitting rod 18
toward the rear end of the lever 4 against the biasing force of the
torque setting spring 22. Namely, the torque limiter starts to
act.
[0051] As the tightening force to the bolt increases, the reaction
force from the torque transmitting cam surface 7a to the roller
member 14 also increases, whereby the roller member 14 moves toward
the cam top against the spring force of the torque setting spring
22. When the roller member 14 goes over the cam top of the cam part
7, the torque limiter is activated whereby the force from the
roller member 14 that rotates the cam shaft 8 in a tightening
direction no longer acts so that the user knows that a specified
torque has been reached.
[0052] After the torque limiter is activated wherein the roller
member 14 has reached the cam top position, the roller member 14
moves on to abut on the torque non-transmitting cam surface 7b, so
that the spring force from the torque setting spring 22 is applied
via the spring force transmitting rod 18 to the roller support
lever member 12 and acts as a rotating force in the clockwise
direction, whereby the force required to apply in the tightening
direction to the lever 4 is suddenly decreased. The lever 4 then
turns idly relative to the bolt until the roller support lever
member 12 comes to the above-described stationary state.
[0053] Now, the relationships between forces that act on various
constituent elements of the torque limiter in the torque wrench of
the present embodiment will be described with reference to FIG.
5.
[0054] In the non-tightened state of the torque wrench 1, where the
roller support lever member 12 is in the above-described stationary
state, the reaction force that acts from the torque transmitting
cam surface 7a to the roller member 14 is denoted by P1. This
reaction force P1 is a force in a normal direction at a position
where the torque transmitting cam surface 7a and the roller member
14 abut each other. In the present embodiment, the vector direction
of this reaction force P1 is displaced by an angle .theta. toward a
bolt tightening direction from the direction of a base line that is
a line connecting the center of the support shaft 16 and the axial
center of the roller member 14.
[0055] Accordingly, when a tightening force is applied during
tightening of a bolt from the roller member 14 to the torque
transmitting cam surface 7a of the cam part 7, a reaction force P2
toward the cam top side along a tangent line between the roller
member 14 and the torque transmitting cam surface 7a acts on the
roller member 14, i.e., a force acts such as to push out the roller
member 14 toward the cam top side. Here, the reaction forces P1 and
P2 satisfy the following relationship:
P2=P1.times.tan .theta. (1).
As is seen from the above equation (1), the smaller the angle
.theta. is between the normal line and base line at the position
where the torque transmitting cam surface 7a and the roller member
14 abut each other, the smaller the force P2 is relative to the
force P1. This force P2 that pushes out the roller member 14 pushes
the roller support lever member 12 toward the rear of the torque
wrench 1, and this force acts on the spring force transmitting rod
18 via the pivot recess 12b.
[0056] On the other hand, the force F that acts from the roller
support lever member 12 to the spring force transmitting rod 18 can
be made even smaller than the force P2 required for the torque
transmitting cam surface 7a to push out the roller member 14.
[0057] This is because the interaxial distance r2 between the axial
center of the support shaft 16 and the center of one spherical end
18a of the spring force transmitting rod 18 is longer than the
interaxial distance r1 between the axial centers of the support
shaft 16 and roller member 14. Namely, since the moment (torque)
around the support shaft 16 is determined by a product of a
distance from the support shaft 16 to a point of application of
force and a force applied, the moment (torque) around the support
shaft 16 at the roller member 14 is equal to the moment (torque)
around the support shaft 16 at one spherical end 18a of the spring
force transmitting rod 18. Therefore, the force F acting at the
position of the longer distance r2 than the distance r1 from the
support shaft 16 is smaller than P2.
[0058] The force F acting on the spring force transmitting rod 18
being smaller than the force P1 means that the force that pushes
back the spring 22 is smaller than P1. This in turn means that the
force the torque setting spring 22 requires to press the roller
support lever member 12 in order to press the roller 14 against the
cam 8 is smaller than P1.
[0059] For this reason, the torque wrench 1 of the present
embodiment can employ a smaller, lighter spring with a lower spring
constant in contrast to conventional ones for the torque setting
spring 22. Also, since the force acting from the roller support
lever member 12 to the spring force transmitting rod 18 and the
force acting from the spring force transmitting rod 18 to the rod
seat 20 are smaller than P1, smaller and lighter components can be
used for the spring force transmitting rod 18 and the rod seat 20,
too. Accordingly, the torque wrench 1 of the present embodiment
provides the effect of enabling reduction in size and weight of the
entire torque wrench 1.
[0060] As described above, the forces P2 and F can be varied by
changing the angle .theta. between the direction of the force P1
(normal direction) and the direction of the base line at the
position where the torque transmitting cam surface 7a of the cam
part 7 and the roller member 14 abut each other. The angle .theta.
is preferably larger than 0.degree. and smaller than
45.degree..
[0061] If the angle .theta. is 0.degree., the force P1 in the
normal direction coincides with the direction of the link, whereby
the roller 14 is merely pushed toward the support shaft 16, and no
component of force that pushes back the roller 14 against the force
of the spring 22 acts on the roller 14. Therefore, the angle should
preferably be not 0.degree. since the torque wrench could then not
function as a torque wrench.
[0062] If the angle is smaller than 0.degree., in other words, if
the direction of the force P1 is on the counterclockwise side of
the base line connecting the support shaft 16 and the roller member
14 in FIG. 5, the force that acts on the roller member 14 acts in
an opposite direction from the direction in which it pushes back
the roller member 14 against the spring force of the torque setting
spring 22. Therefore, this is not preferable either since, in this
case, the torque wrench 1 could not function as a torque
wrench.
[0063] If the angle .theta. is larger than 45.degree., the force P1
in the normal direction becomes equal to the force P2, which
lessens the effect of reducing the force required to apply to the
torque setting spring 22 by the function of the roller support
lever member 12, and thus is not preferable.
[0064] The angle .theta. between the direction of the base line and
the direction of the force P1 (normal direction) may be adjusted by
changing the positional relationship between the support shaft 16
and the roller member 14 thereby to vary the length in the base
line direction, or by changing the curved surface shape of the
torque transmitting cam surface 7a of the campart 7. For example,
disposing the support shaft 16 at a position further toward the
distal end of the head portion 2 than the position illustrated in
FIG. 5 increases .theta., which in turn increases P2. The angle
.theta. can also be made smaller by increasing the inclination of
the slope of the torque transmitting cam surface 7a abutting on the
roller member 14 in the non-tightened state, as the normal line
direction is thereby made closer to the base line direction.
Conversely, decreasing the above-mentioned inclination increases
.theta..
[0065] In the torque wrench 1 of the present embodiment, similarly,
the force that acts on the torque setting spring 22 can be varied
by changing the distance r2 between the support shaft 16 and the
pivot recess 12b (i.e., the point of engagement of one spherical
end 18a of the rod 18). For example, setting the pivot recess 12b
at a position farther away from the support shaft 16 so that the
interaxial distance r2 is longer than that illustrated in FIG. 5
makes F smaller, since, as described above, the moment around the
support shaft 16 is the same. Note, however, increasing the
interaxial distance r2 too much obviously leads to an increase in
size of the roller support lever member 12 and, in turn, of the
head portion 2.
[0066] Increasing the interaxial distance r2 also leads to a larger
displacement (in the Y-axis direction) between the position of the
pivot recess 12b and the position of the pivot recess 20a of the
rod seat 20 in the non-tightened state. This in turn results in a
larger inclination of the spring force transmitting rod 18 relative
to the X-axis direction of the torque wrench 1 in the non-tightened
state. Applying a force to the rod 18 in this state causes a larger
component of force in the Y-axis direction of the force to act on
the rod seat 20. This component of force in the Y-axis direction
presses the rod seat 20 against the inner surface of the lever 4
and increases friction, which may cause a decrease in torque
measurement precision and is not preferable.
[0067] As described above, according to the torque wrench 1 of the
present embodiment, the torque limiter is configured such that, the
solid columnar roller member 14 abutting on the cam part 7 of the
cam shaft 8 is rotatably disposed in the bearing recess 12a of the
roller support lever member 12, and such that the force acting
against the force of the torque setting spring 22 can be made
smaller than the force along the normal direction acting from the
torque transmitting cam surface 7a to the roller member 14. This
enables reduction in size and weight of the components such as the
torque setting spring 22 and the spring force transmitting rod 18
that couples the roller support lever member 12 with the torque
setting spring 22. Accordingly, a small, light-weight torque wrench
can be provided.
[0068] In a torque wrench with a torque limiter configured using a
conventional cam mechanism disclosed in the specification of
British Patent Application Laid-Open No. 2148767A, in which a cam
follower roller or the like is pressed against a cam directly with
a spring, there is a friction between the roller and the inner
surface of the head or lever as the rotating roller slides along a
torque transmitting cam surface of the cam. In contrast, according
to the torque wrench 1 of the present embodiment, the roller member
14 is supported by the roller support lever member 12 which is
pivotable around the support shaft 16, so that there is no friction
between the roller member 14 and the inner surface of the head
portion 2 or the lever 4. Accordingly, a torque wrench wherein
friction during the operation is reduced as compared to the
above-mentioned conventional torque wrench can be provided.
[0069] In the present embodiment, the spring force transmitting rod
18 has been described to have an engagement structure using a
spherical surface and a recess that enable a pivoting action
between the spring force transmitting rod 18 and the roller support
lever member 12 and the rod seat 20. The present invention is not
limited thereto. As described above, in the torque wrench 1 of the
present embodiment, the tracing action of the roller member 14
along the cam surface of the cam part 7 takes place within the X-Y
plane shown in FIG. 5. Therefore, shafts may be extended at both
ends of the spring force transmitting rod 18 so that they engage
with the roller support lever member 12 and the rod seat 20 such as
to be pivotally supported, or, a disk-like engagement portion may
be configured that slides only in a circumferential direction
within the X-Y plane.
Embodiment 2
[0070] FIG. 6 and FIG. 7 are plan views showing the internal
structure of a torque wrench 100 according to Embodiment 2 of the
present invention by a partial cross section. The elements
identical to those shown in FIG. 1 to FIG. 5 are given the same
reference numerals and will not be described again.
[0071] The torque wrench 100 of the present embodiment includes a
torque limiter shown in Embodiment 1, and a function for
electrically detecting the tightening torque of the bolt having
reached a specified torque based on the activation of the torque
limiter, utilizing the fact that the spring force transmitting rod
18 held between the opposing pivot recesses 12b and 20a changes its
orientation from being parallel to inclined relative to the X-axis
direction because of a rotation of the roller support lever member
12 upon the start of activation of the torque limiter during
tightening of the bolt.
[0072] According to the torque wrench 100 of the present
embodiment, during a tightening operation using a torque wrench of
the type shown in Embodiment 1, the completion of tightening with a
specified torque can be detected by an electrical signal.
Therefore, using this signal, for example, the user may be notified
of the completion of tightening with a sound, light, or the like,
or, the number of tightening may be counted by outputting the
signal indicative of the completion of tightening to an external
information processing device. Accordingly, with the torque wrench
100 of the present embodiment, the tightening operation can be
managed, for example, by checking whether there has been any bolt
left untightened, or the like.
[0073] The torque wrench 100 of the present embodiment includes a
sensor 30 disposed on the outer circumference of the cylindrically
formed lever 4 for detecting the spring force transmitting rod 18
having reached a predetermined inclination angle. A microswitch
having a mechanical switching configuration is used for the sensor
30. An opening 4a is formed to a portion of the circumferential
wall of the lever 4 corresponding to the sensor (hereinafter
described as a microswitch) 30, with a switch operating lever 30a
of the microswitch 30 making contact with an outer circumferential
surface of the spring force transmitting rod 18 inside the lever 4
through this opening 4a.
[0074] When the tightening of the bolt starts, the spring force
transmitting rod 18 starts to incline from the non-tightened state
shown in FIG. 6 where it is parallel to the X-axis. As the
inclination of the spring force transmitting rod 18 is increased,
the switch operating lever 30a is inclined toward a direction in
which it pushes in a switch element (not shown). When the spring
force transmitting rod 18 reaches a maximum inclination angle at
which the torque limiter is activated, as shown in FIG. 7, the
microswitch 30 is switched from OFF state to ON state, thereby
outputting a detection signal to an external device through a cord
34 connected to the sensor 30. The microswitch 30 is accommodated
inside an outer case 32, which protects the microswitch 30 as well
as prevents dust or dirt from entering into the lever 4 through the
opening 4a. By this ON signal thus output, the completion of one
tightening operation with a specified torque can be detected.
[0075] As described above, according to the torque wrench 100 of
the present embodiment, a tightening completion signal indicative
of the completion of tightening of a fastener such as a bolt with a
specified torque can be output to an external device. Accordingly,
the number of tightened bolts can be counted to check if there is
any bolt left untightened.
[0076] While a limit switch is used for the sensor 30 in the torque
wrench 100 of the present embodiment, the invention is not limited
to this. Any type of sensor or switch that can detect a change in
the inclination of the rod 18 can be used, such as sensors using
magnetism, laser, ultrasonic sound, or the like.
[0077] While the sensor 30 was described as being disposed on a
lateral surface on one side of the Y-axis direction of the lever 4
in the present embodiment, the invention is not limited to this. It
may be disposed at any position as long as it can determine a
change in the inclination of the rod 18.
Embodiment 3
[0078] FIG. 8 is a sectional view showing the entire configuration
of a torque wrench according to Embodiment 3. The elements
identical to those of the reference numerals described above and
shown in FIG. 1 are given the same reference numerals in FIG. 8 and
will not be described again.
[0079] While the roller 14 is solid and columnar in Embodiment 1
shown in FIG. 1, in the embodiment shown in FIG. 8, the roller 14
is formed by a hollow cylindrical roller body 14a and a roller
shaft 14b supported at both ends by the roller support lever member
12, such that the roller shaft 14b rotatably extends through the
roller body 14a.
[0080] In FIG. 8, similarly to Embodiment 1 shown in FIG. 3, a
large number of steel balls 9a and 9b are disposed between the
outer circumferential surface of the cam shaft 8 and the inner
circumferential surface of the head portion 2, respectively, to
form radial bearings at upper and lower parts of the cam shaft 8.
Instead, the cam shaft 8 may be supported relative to the head
portion 2 by a rolling bearing having a ring-like inner race, a
ring-like outer race, and a plurality of rolling elements such as
steel balls or rollers disposed between the inner and outer races.
In this case, the inner races are respectively mounted to the upper
and lower parts of the cam shaft 8, whereas the outer races are
attached to the inner circumferential surface of the head portion
2. This rolling bearing may be applied to Embodiment 1 described
above, too.
Embodiment 4
[0081] FIG. 9 is a partially cut-away sectional view showing the
detail of a coupling mechanism for coupling the head and the lever
of a torque wrench according to Embodiment 4 of the present
invention.
[0082] In the embodiment shown in FIG. 6 and FIG. 7, the inclining
movement of the spring force transmitting rod 18 is used to turn on
the microswitch 30 so as to enable electrical detection of the
activation of the torque limiter. In this case, the lever 4 to
which the microswitch 30 is secured and the head 2 need to be
coupled together at a predetermined position in the circumferential
direction around the center axis line of the lever 4 as the center,
so that the spring force transmitting rod 18 can be inclined to a
position where it turns on the microswitch 30 at the exact moment
when the torque limiter is activated.
[0083] In FIG. 9, the distal end of the cylindrically formed lever
4 is formed by a threaded tube portion 15a formed with a male
threaded portion on the outer circumferential surface, and a thin,
cylindrical, tubular spreading portion 15b continuously formed to
the front of the threaded tube portion 15a. The tubular spreading
portion 15b is formed thin to have a smaller diameter than the
outside diameter of the threaded tube portion 15a, and its distal
end inner circumferential surface (referred to as "tapered female
engaging portion") 15c is formed in a horn-shape, with the inner
diameter gradually increasing toward the distal end.
[0084] The inner circumferential surface of the threaded tube
portion 3b of the head 2 is formed with a first female threaded
portion 15d into which the threaded tube portion 15a of the lever 4
is screwed, and a second female threaded portion 15e located more
forward than the first female threaded portion 15d. A cylindrical
positioning member 17 is screwed into this second female threaded
portion 15e.
[0085] The positioning member 17 is composed of a threaded portion
17b formed on the outer circumference to be screwed into the second
female threaded portion 15d, a tapered pressing portion (tapered
male engaging portion) 17a formed at the rear of the threaded
portion 17b to abut and make, tapered engagement with the tapered
female engaging portion 15c, and an engaging hole (hexagonal hole)
17c formed in a center hole portion to engage with, for example, a
hexagonal wrench (not shown). The spring force transmitting rod 18
extends through this hexagonal hole 17c. The pressing portion 17a
is formed to have a tapered surface with the outside diameter
gradually decreasing from the distal end side toward the rear end
side.
[0086] Before screwing the threaded tube portion 15a of the lever 4
into the first female threaded portion 15d of the threaded tube
portion 3b of the head 2, the positioning member 17 is first
screwed into the second female threaded portion 15e. The first and
second female threaded portions 15d and 15e may be formed as one
female threaded portion.
[0087] The position at which the spring force transmitting rod 18
extends through the engaging hole 17c varies because the position
of the pivot recess 12a changes in accordance with the action of
the roller support lever member 12, as described above. Therefore,
the engaging hole 17c is designed to have such an inside diameter
that the spring force transmitting rod 18 does not contact it even
though its position changes in accordance with the action of the
roller support lever member 12.
[0088] The structure of the coupling mechanism 13 of the present
embodiment is as described above. Below, the method of positioning
and fixing the head 2 and the lever 4 in their circumferential
direction will be described.
[0089] With a torque wrench of the type that screw-couple the
cylindrical head 2 and the lever 4 as the torque wrench 1, a firm
coupling can be achieved relative to the operation of tightening a
fastener. Nevertheless, depending on how the screw is threaded or
how the head 2 and the lever 4 are tightened, there are variations
in relative positional relationship between them in the
circumferential direction when they are screw-coupled. The torque
wrench 1 of the present embodiment, by means of the positioning
member 17, can precisely determine their coupling position in the
circumferential direction. More specifically, as shown in FIG. 6,
they are positioned such that the opening 4a for the microswitch 30
coincides with the Y-axis.
[0090] The coupling method involves, first, screwing the
positioning member 17 into the second female threaded portion 15e
inside the threaded tube portion 3b of the head 2 as described
above to the farthest end in the direction of the distal end of the
head 2. The threaded tube portion 15a of the lever 4 and the first
female threaded portion 15d of the threaded tube portion 3b of the
head 2 are screwed and coupled to each other. As the lever 4 is
screwed into the head 2, the tapered female engaging portion 15c
formed at the distal end of the lever 4 abuts and makes tapered
engagement with the pressing portion 17a of the positioning member
17. The spreading portion 15b of the lever 4 is then gradually and
elastically pushed open as mentioned above by the wedge effect so
that it is pressed against the inner circumferential surface of the
threaded tube portion 3b of the head 2, whereby the head 2 and the
lever 4 are tightened to each other. After being tightened to some
degree, the head 2 and the lever 4 are adjusted to a desired
position in the circumferential direction in which they are
tightened.
[0091] Next, a hexagonal wrench is inserted from the opening in the
case portion 3a provided for mounting the cam 8, transmission shaft
11, and the like, so as to turn the positioning member 17 to
advance along the thread toward the lever 4. This causes the
pressing portion 17a of the positioning member 17 abutting on the
tapered female engaging portion 15c of the spreading portion 15b of
the lever 4 to further push open the spreading portion 15b. In this
way, the distal end 4b of the lever 4 is pressed against the
coupling portion 2b of the head 2, whereby the head 2 and the lever
4 are rigidly coupled together. The torque wrench 1 can be
eventually assembled by mounting components such as the cam part 7
into the case portion 3a after the positioning and fixing made in
this way.
[0092] The head 2 and the lever 4 are thus tightened and coupled
together to such an extent that a sufficient strength can be
secured for the tightening operation, and further, with their
positions in the circumferential direction in which they are
screw-tightened relative to each other being adjusted to a desired
position, the positioning member 17 is advanced along the thread
toward the lever 4 so that they are further rigidly tightened and
fixed together. Thereby, the head 2 and the lever 4 are rigidly
coupled together with their positions precisely set at a
predetermined position in the circumferential direction.
[0093] The positioning member 17 of the present embodiment is
screwed inside the head 2, as described above, so that it cannot be
manipulated easily after the torque wrench 1 is assembled.
Therefore, there is no accidental displacement thereof and
consequent misalignment in the coupling position during use of the
torque wrench 1.
[0094] As described in Embodiment 2, the start of the tightening of
the torque wrench 1 initiates activation of the torque limiter,
turning the roller support lever member 12 around the support shaft
16, and when the torque limiter changes its orientation from the
non-activated state shown in FIG. 6 to the activated state shown in
FIG. 7, the spring force transmitting rod 18 changes its
inclination relative to the X-axis direction.
[0095] In the present embodiment, the head 2 and the lever 4 are
positioned and fixed to each other by the coupling mechanism 13
such that the spring force transmitting rod 18 and the switch
operating lever 30a of the microswitch 30 both move parallel to the
X-Y plane.
[0096] Namely, in the non-activated state shown in FIG. 6 before
the specified torque is reached, the microswitch 30 is OFF, while,
in the torque limiter-activated state shown in FIG. 7, the rod 18
is inclined maximum in the X-Y plane, whereby the switch operating
lever 30a is pushed to turn on the microswitch 30. After that, the
roller member 14 moves on to the position of the next cam part 7
thereby rendering the torque limiter non-activated and turning off
the microswitch 30. With the ON signal thus output, the completion
of one tightening operation with a specified torque can be
detected. Here, the switch operating lever 3a is moved by the
inclining movement of the spring force transmitting rod 18 at the
same time when the torque limiter is activated, so that the ON
signal can be output precisely.
[0097] Without the coupling mechanism 13, the positional
relationship between the head 2 and the lever 4 in the coupled
state can still be determined to some extent by determining the
length of the threaded portions and the threading starting position
for the screw coupling. There are, however, variations depending on
how they are tightened or on the forming precision of the thread
grooves.
[0098] As described above, according to the present embodiment, in
the case where a microswitch 30 is mounted to the lever 4 for
detecting the change in inclination of the spring force
transmitting rod 18 in order to detect the completion of
tightening, the head 2 and the lever 4 can be precisely positioned
to each other in the circumferential direction, and the completion
of tightening with a specified torque can be reliably detected in
accordance with the activation of the torque limiter. Accordingly,
the number of tightened bolts can be precisely counted to check if
there is any bolt left untightened, or the like.
[0099] The torque wrench having the cam shaft 8, the roller support
lever member 12, the roller member 14, and the spring force
transmitting rod 18 was described as one example in the present
embodiment as a torque wrench 1 having the head 2 and the lever 4
coupled together by screw threading, but the invention is not
limited to this. The positioning member according to the present
invention can be applied to any type of torque wrench, as long as
it is a torque wrench of the type having a head and a lever
screw-coupled to each other, wherein their relative positional
relationship in the circumferential direction needs to be
determined. The positioning member is not to be limited by the
mechanism itself for tightening with a predetermined torque.
[0100] Also, while a torque wrench of the type that has the head 2
and the lever 4 tightened together by screw engagement between an
inner circumferential surface of the head 2 and an outer
circumferential surface of the lever 4 was described in the present
embodiment, the invention is not limited to this. For
example,thread grooves may be formed in the outer circumferential
surface of the head and in the inner circumferential surface of the
lever to screw-couple them together. In this case, the positioning
member 17 is screwed into the inner circumferential surface of the
lever 4 such that the tapered portion 3a is directed toward the
head 2. After screw-coupling the lever 4 with the head 2 and
positioning them at a predetermined position, the positioning
member 17 is advanced along the thread toward the head 2. This
pushes the head 2 open relative to the lever 4, so that they can be
rigidly fixed together in their position-adjusted state.
Embodiment 5
[0101] FIG. 10 is a partial sectional view showing the detail of
another coupling mechanism for coupling the head and the lever of a
torque wrench according to Embodiment 5 of the present
invention.
[0102] The coupling mechanism 130 of the present embodiment is
configured such that, the threaded tube portion 15a provided at the
distal end of the lever 4 is screwed into a female threaded portion
formed on the inner circumferential surface of the threaded tube
portion 3b of the head 2, and a nut-like positioning member 170
screwed on the outer circumference of the threaded tube portion 15a
of the lever 4 is advanced along the thread forward as indicated by
arrow A so as to position and fix the lever 4 and the head 2 in a
circumferential direction around the X-axis.
[0103] The threaded tub portion 3b of the head 2 is formed at the
rear end thereof with a tightened portion (tapered male engaging
portion) formed as a tapered surface, this tightened portion 300
being formed as a tapered surface with its outside diameter
gradually decreasing toward the rear. The nut-like positioning
member 170 is formed with a tightening portion (tapered female
engaging portion) 170c having a horn-like inner circumferential
surface to the front of the female threaded portion 170b screwed
onto the threaded tube portion 15a, the tightened portion 300
forming a tapered surface abutting and making tapered engagement
therewith.
[0104] The positioning and fixing by the coupling mechanism 130 of
the present embodiment is achieved by first screwing the
positioning member 170 onto the outer circumferential surface of
the lever 4 and then by screw-coupling the lever 4 with the head 2.
After positioning the head 2 and the lever 4 at a predetermined
position in the circumferential direction, the positioning member
170 is advanced along the thread toward the head 2 (in the
direction of arrow A). This causes the tightening portion 170c to
press the tightened portion 300 of the head 2 against the outer
circumferential surface of the threaded tube portion 15a of the
lever 4, whereby the head 2 and the lever 4 are rigidly coupled
together.
[0105] In the case with using this positioning member 170, the
coupling portion between the head 2 and the lever 4 may have a
configuration wherein they are coupled together with the outer
circumferential surface of the head 2 being screwed to the inner
circumferential surface of the lever 4. In this case, the
positioning member 170 may be advanced along the thread from the
head 2 side toward the lever 4 to press the lever 4 against the
head 2, whereby they can be rigidly positioned and fixed.
Embodiment 6
[0106] FIG. 11 shows Embodiment 6 of the present invention. The
elements identical to those shown in FIG. 8 are given the same
reference numerals and will not be described again.
[0107] In the coupling mechanism 13 or 130 of the above Embodiment
4 or 5, the positioning member 17 or 170 makes tapered engagement
with a distal end portion of the lever 4 or a rear end portion of
the threaded tube portion 3b of the head portion 2. Instead of the
above tapered engagement, in the coupling mechanism 230 of the
present embodiment, the lever 4 and the head portion 2 are coupled
together with a double nut structure wherein a rear end face of the
positioning member 270 is made abut against and tightened to a
distal end face of the lever 4.
[0108] In FIG. 11, similarly to the positioning member 17 of FIG.
8, the positioning member 270 is formed with a hexagonal hole 17c
and a threaded portion 17b on the outer circumferential surface
thereof, while its rear end face is formed as a flat surface
extending along the Y-axis direction.
[0109] The first female threaded portion 15d screwed to the
threaded tube portion 15a formed at the distal end of the lever 4
and the second female threaded portion 15e screwed to the threaded
portion 17b of the positioning member 270 are formed as a common
female threaded portion on the inner circumferential surface of the
threaded tube portion 3b.
[0110] The distal end of the threaded tube portion 15a of the lever
4 has a constant outside diameter up to the distal end, with a
threaded portion screwed into the first female threaded portion 15d
being formed on the outer circumferential surface thereof. The
distal end face 15f of the threaded tube 15d is formed as a flat
surface extending along the Y-axis.
[0111] With the coupling mechanism 230 of the present embodiment,
similarly to Embodiment 4, the positioning member 270 is first
screwed into the second female threaded portion 15e. Then, the
lever 4 is turned and screwed in, to cause the threaded tube
portion 15a of the lever 4 to screw into the first female threaded
portion 15d of the threaded tube portion 3b of the head 2. The
lever 4 is screwed in until the rear end face 17d of the
positioning member 270 contacts the distal end face of the threaded
tube portion 15a, and turned around the X-axis direction to a
predetermined position relative to the head portion 2. In this
state, the positioning member 270 is turned using a hexagonal
wrench similarly to Embodiment 4 to advance it along the thread to
the rear end side, so that the rear end face of the positioning
member 270 is firmly pressed against the distal end face of the
threaded tube 15d, whereby the positioning member 270 acts as a
lock nut for the threaded tube 15d. The lever 4 is thus coupled to
the head portion 2.
[0112] The coupling mechanism of the present embodiment may be
applied to the configuration of Embodiment 5 shown in FIG. 10.
[0113] While the present invention has been described in detail by
way of particular embodiments thereof, it will be apparent to those
skilled in the art that various changes and modifications could be
made without departing from the spirit and scope of the present
invention.
[0114] As described above in detail, according to the present
invention, in a torque wrench with a torque limiter having a
configuration in which the principle of leverage is used to cause a
cam follower in the form of a solid columnar roller to make
pressure contact with a cam that transmits a tightening force to a
fastener such as a bolt or nut when tightening the same with a
spring pressure of a torque setting spring, a technique that
realizes more stable operation and enables highly precise
tightening can be provided.
DESCRIPTION OF REFERENCE NUMERALS
[0115] 1, 100 Torque wrench [0116] 2 Head portion [0117] 3a case
portion 3b threaded tube portion 3c lid [0118] 3d upper wall
portion 3e, 3f, 3g, 3h hollow part [0119] 4 Lever [0120] 5 shaft
hole [0121] 6 Grip [0122] 7 Cam part [0123] 7a torque transmitting
cam surface 7b torque non-transmitting cam surface [0124] 8 Cam
shaft [0125] 8a shaft hole 8b upper circumferential groove 8c lower
circumferential groove 8d ratchet teeth [0126] 9a, 9b, 9c Steel
ball [0127] 10 Ratchet claw [0128] 11 Transmission shaft [0129] 11a
main shaft 11b square shaft [0130] 12 Roller support lever member
[0131] 12a bearing recess 12b pivot recess [0132] 13, 130, 230
Coupling mechanism [0133] 14 Roller member [0134] 15a Threaded tube
portion 15b spreading portion 15c tapered female engaging portion
[0135] 15d First female threaded portion 15e second female threaded
portion [0136] 16 Support shaft [0137] 17, 170, 270 Positioning
member [0138] 17a pressing portion 17b threaded portion 17c
hexagonal hole [0139] 18 Spring force transmitting rod [0140] 20
Rod seat [0141] 20a pivot recess [0142] 21 Adjusting nut [0143] 22
Torque setting spring [0144] 24 Torque adjusting screw rod [0145]
25 Steel ball [0146] 26 Bearing recess [0147] 30 Microswitch [0148]
300 Tightened portion
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